C8 - Host Microorganisms Interactions (Part 2) Flashcards
HOST RESISTANCE
Physical Barriers
Macrophages
Physical Barriers
a. Healthy, Intact Skin
b. Cleansing Mechanisms
c. Antimicrobial Substances
d. Indigenous Microbial Flora
e. Phagocytosis
→ primary mechanical barrier to infection
Healthy, Intact Skin
→has substantial numbers of microbial flora that contribute to a low pH, compete for nutrients, and produce bactericidal substances addition
Healthy, Intact Skin
→ ensures that relatively few organisms can survive and prosper in the acid environment
low pH resulting from long-chain fatty acids secreted by sebaceous glands
Spp capable of penetrating normal, healthy skin
Leptospira spp., Francisella tularensis, Treponema spp
Mechanism of urethral opening as a barrier
Stricture
This action allows the urethra to be less susceptible to microorganism growth
urination
Found in the cervical opening that acts as a barrier for microorganism
thick mucus plug
What natural process involves the shedding of the skin surface to remove potential pathogens?
Desquamation
What two antimicrobial components are found in tears?
IgA and lysozyme
How does the respiratory tract help remove trapped microbes?
Mucus traps particles and sweeps them to the oropharynx.
What type of epithelium lines the trachea and aids in clearing particles upward?
Ciliated epithelium
Which reflex helps expel potentially infected agents from the respiratory system?
Cough-sneeze reflex
What two mechanisms in the gastrointestinal tract prevent organisms from attaching to the intestinal epithelium?
Mucous secretions and peristalsis
What cleansing action in the genitourinary tract helps prevent infection?
Voiding urine
What characteristic of the vagina inhibits colonization by transient organisms?
Acidity
Cleansing Mechanisms of the body
Desquamation
IgA and lysozyme in tears
Mucus in RT
Ciliated epithelium in trachea
Cough-sneeze reflex
Mucous secretions and peristalsis of the GI tract
Voiding urine
Acidity of vagina
Antimicrobial Substances
Lysozyme
Secretory IgA
β-lysins
Interferon
→low-molecular-weight (approximately 20,000 D) enzyme that hydrolyzes the peptidoglycan layer of bacterial cell walls
Lysozyme
Lysozyme found in
serum,
tissue fluids,
tears,
breast milk,
saliva, and
sweat
→serve as opsonins, fix complement and neutralize the infecting
organism
Secretory IgA
Secretory IgA →found in
mucous secretions of the
respiratory,
genital, and
digestive tracts
Secretory IgA serve as
opsonins
→low-molecular-weight cationic proteins in serum
→lethal against gram-positive bacteria and are released from platelets during coagulation
β-lysins
→inhibits proliferation of viruses
Interferon
→compete with pathogens for nutrients and space
Indigenous Microbial Flora
→substances that inhibit the growth of closely related bacteria
Bacteriocins
→process by which phagocytes engulf and dispose of microorganisms and cell debris
Phagocytosis
necessary for the killing and digestion of the engulfed particles
Lysosomes
Lysosomes [enumerate]
myeloperoxidase,
proteases,
cathepsin,
lactoferrin,
lysozyme, and
elastase
→has receptors on the cell membrane for some complement components that stimulate cell motion, the metabolic burst, and secretion of the lysosome contents into a phagosome
PMN - polymorphonuclear leukocyte
PMN circulating half life hours
2-7 hours
PMN may migrate to the tissues where their half life is
less than a week
→circulate as monocytes for 1 to 2 days and then migrate through the blood vessel walls into the tissues and reside in specific tissues as part of the MONONUCLEAR PHAGOCYTE SYSTEM
Macrophages
Macrophages are part of the [system]
MONONUCLEAR PHAGOCYTE SYSTEM
→widely distributed in the body and play a central role in specific immunity and nonspecific phagocytosis
Macrophages
Chemotaxis two types
Diapedesis
Chemotaxis
→ movement of the neutrophils between the endothelial cells of the blood vessels into the tissues
DIAPEDESIS
→directed migration of PMNs into the area of infection
CHEMOTAXIS
→facilitated by the binding of specific antibodies to the microorganism
Attachment
→coating of the bacterium with antibody or complement components results in enhanced phagocytosis by the PMN
OPSONIZATION
Neutrophils have membrane receptors for?
Fc region of
IgG1
IgG3
C3b component of complement
Which antibody classes can bind to organisms to initiate opsonization?
IgG1 or IgG3
What happens when the antibody response is insufficient for opsonization?
Complement is fixed on the surface of the organism
Which pathway can be activated by endotoxins or polysaccharides for opsonization?
Alternative complement pathway
✓Cell membrane of the phagocytic cell invaginates and surrounds the attached particle
Ingestion
In Ingestion ✓Particle is taken into the cytoplasm and enclosed within a
vacuole called a
PHAGOSOME
✓Phagosome fuses with lysosomes
PHAGOLYSOSOME
Lysosomes release their contents into the phagosome
DEGRANULATION
Ingestion included enzymes
proteases,
lipases,
RNase,
DNase,
peroxidase, and
acid phosphatase
→phagocytosis of a particle triggers a significant increase in the metabolic activity of the neutrophil or macrophage
Metabolic or Respiratory Burst
Killing / Metabolic or Respiratory Burst increases in
glycolysis
→body’s response to injury or foreign
body
Inflammation
→hallmark of inflammation:
accumulation of large numbers of
phagocytic cells
→leukocytes release mediators or
cause other cell types to release which cause ______________ as a result of greater blood flow, edema from an increase in vascular permeability, and
continued phagocyte accumulation,
resulting in ____________
erythema
pus
CARDINAL SIGNS OF INFLAMMATION
SWELLING,
REDNESS,
HEAT,
PAIN,
LOSS OF FUNCTION
Chemical Mediatiors of Inflammation:
✓Histamine
✓Kinins
✓Leukotrienes
✓Prostaglandins
✓Acute phase reactants
✓Cytokines
✓Acute phase reactants examples
CRP,
Serum amyloid A,
antitrypsin,
fibrinogen
✓Cytokines that mediate inflammation
IL-1,
IL-6,
TNF-α,
IFN-γ,
IL-2
→mechanism whereby the body is able to protect itself from invasion by disease causing organisms
Immunity
→consists of numerous cells and protein molecules that are responsible for recognizing and removing these foreign substances
Immune system
Immune system Divided into two broad categories
Innate or Natural immunity
Adaptive or Specific
little or no specificity immune system
Innate or Natural immunity
highly specialized immune system
Adaptive or Specific
Cells of the immune system
B Lymphocytes (B Cells)
T Lymphocytes (T Cells)
Natural Killer Cells (NK Cells)
B Lymphocytes (B Cells) Location
Lymphoid tissues (lymph nodes, spleen, gut- associated lymphoid tissue, tonsils)
B Lymphocytes (B Cells) Function
Antibody-producing cells
B Lymphocytes (B Cells) Subtypes
B lymphocytes
B-memory cells
Plasma cells
Cells waiting to be stimulated by an antigen
B lymphocytes
Activated B lymphocytes that secrete antibody in response to an antigen
Plasma cells
Long-lived cells preprogrammed to antigen for subsequent exposure
B-memory cells
T Lymphocytes (T Cells) Location
Circulate and reside in lymphoid tissues (lymph nodes, spleen, gut-associated lymphoid tissue, tonsils)
T Lymphocytes (T Cells) Subtypes:
Helper T cells
Cytotoxic T cells
Suppressor T cells
Interact with B cells to facilitate antibody production
Helper T cells
Recognize and destroy host cells that have been invaded by microorganisms
Cytotoxic T cells
Mediate regulatory responses within the immune system
Suppressor T cells
Similar to that of cytotoxic T cells; however do not require the presence of an antigen to stimulate function
Natural Killer Cells
Immediate response to the pathogen that does not confer long lasting protective immunity
INNATE, OR NATURAL,
NONSPECIFIC IMMUNITY
INNATE, OR NATURAL,
NONSPECIFIC IMMUNITY examples
Physical and chemical barriers
Blood proteins
phagocytosis
Blood proteins that act as
mediators of infection
Cytokines,
Complement
→capable of being specific for distinct molecules, responding in particular ways to different types of foreign substances and developing memory, which allows for a more vigorous response to repeated exposures to the same foreign invader
ADAPTIVE, OR SPECIFIC IMMUNITY
2 types of ADAPTIVE, OR SPECIFIC IMMUNITY
Humoral or Cellular Immune Response
major constituents of the adaptive or specific immune response
Lymphocytes and Antibodies
able to remember each time it encounters a particular foreign antigen
Immunologic Memory
→Antibody mediated
. HUMORAL IMMUNE RESPONSE
Immunoglobulin G (IgG) percent of the total serum immunoglobulin pool
→70% to 75%
Immunoglobulin G (IgG) halflife in serum
3 to 4 weeks
→cross the maternal placenta to the
fetus
→ passive immunity for newborns,
neutralization of viruses and exotoxin;
responds best to protein antigens, mainly involved in secondary (anamnestic) immune response
Immunoglobulin G (IgG)
→ cannot cross the placenta
→consists of five basic subunits—each composed of two heavy chains and two light chains (similar to an IgG molecule) and linked to another polypeptide chain (J chain) by disulfide bonds
→endotoxin neutralization, bacterial agglutination, complementmediated bacteriolysis, strong opsonization ability; responds best to polysaccharide antigens, mainly involved in primary immune response
Immunoglobulin M (IgM)
Immunoglobulin M (IgM) percent of igms
10%-15%
Immunoglobulin M (IgM) half-life in serum
5 days
→predominant immunoglobulin class in certain body secretions, such as saliva, tears, and intestinal secretions
→ prevention of bacterial and viral invasion of mucous membranes through interference with adherence of
microorganism to site; found in tears, milk, saliva, and respiratory and GI secretions
Immunoglobulin A (IgA)
Immunoglobulin A (IgA) percent
15% to 20%
IgA occurs when
two subunits (each similar to an IgG molecule) linked together by a J chain
contains a secretory component that stabilizes the molecule
Secretory IgA
→increase during infection by numerous parasites and may play a
role in eliminating these infectious agents from the host
→major role in allergic response
Immunoglobulin E (IgE)
→little is known; may serve as a B-cell receptor or play a role in autoallergic diseases
Immunoglobulin D (IgD)
relatively rapid appearance of IgM antibodies
Primary immune response
Antibody Responses
Primary and Secondary
→rapid increase in IgG antibody associated with higher levels, a prolonged elevation, and a more
gradual decline
Secondary or Anamnestic immune response
→based on the action of specific kinds of T-lymphocytes that directly attack the cells that are infected with virus, parasites, cancer cells or transplanted cells
CELL-MEDIATED IMMUNE RESPONSE
→ primary effector cell in cell-mediated immunity
T Lymphocyte
→low-molecular-weight proteins resulting from antigen binding, activation, cell division, and differentiation of the T cell
Lymphokines
Mechanisms by Which Microbes May Overcome Host Defenses
a. Bringing about tolerance
b. Immunosuppression
c. Change in the appropriate target for the immune response
d. Antigenic variation
inability to induce an immune response to a microbial antigen
Tolerance
Antigenic variation example
Borrelia recurrentis
✓Most pathogen are acquired from
external sources
Pathogens usually exit the infected patient most frequently from the
respiratory tract and gastrointestinal
tract
transmission to the new host usually occurs via
airborne respiratory droplets or fecal contamination of food and water
Four (4) important portals of entry for pathogenic organisms
GIT, GUT, respiratory tract, integumentary system
Mucous membranes of the GIT, GUT, repiratory tract and conjunctiva
DISEASES
conjunctivitis, trachoma, ophthalmia
neonatorum
punctures, injections, bites, cuts, wounds, surgery, and splitting of the skin or mucus membrane due to swelling or drying
✓Parenteral route
some organisms have many portals of entry
(Yersinia and B. anthracis)
ROUTES OF TRANSMISSION
- Airborne Transmission
- Transmission by Food and Water
- Close Contact
- Cuts and Bites
- Arthropods
- Zoonoses
Respiratory Spread
→ common
→aerosolized by coughing, sneezing, and talking
Airborne Transmission
—inhalation of infectious particles in liquid droplet dxs
TB,
Brucellosis,
Tularemia,
Legionellosis and
Plague
→residue from the evaporation of fluid from larger droplets and are light enough to remain airborne for long periods
Droplet Nuclei
→infection occurs via the fecal-oral route
Transmission by Food and Water
Transmission by Food and Water spp
Enterotoxigenic E. coli (ETEC)
Vibrio cholera
Enterotoxigenic E. coli is the common cause of
TRAVELER’S DIARRHEA
→enterotoxin that causes the outpouring of fluid from the cells into the lumen of the intestine
Vibrio cholera
Preformed toxins [spp] [fecal oral route]
Clostridium botulinum,
Bacillus cereus, and
S. aureus
→passage of organisms by salivary, skin, and genital contact
Close Contact
→infection by the mouth flora
Cuts and Bites
→dog-bite and cat-bite infections
Pasteurella multocida
→tick, flea, or mite bite
Arthropods
Arthropods dxs
→relapsing fever,
plague,
Rocky Mountain spotted fever,
Lyme disease,
typhus
→depends on contact with animals or animal products
→arthropod vectors (plague), contact with secretions (brucellosis), and contact with animal carcasses and products (tularemia, listeriosis)
Zoonoses
Respiratory Tract pathogens
Streptococcus pneumoniae
Neisseria meningitides
Haemophilus influenzae
Mycobacterium tuberculosis
Bordetella pertussis
Salmonella typhi
Salmonella enteric
Vibrio cholera
Brucella spp
Streptococcus pneumoniae disease
Pneumonia
Neisseria meningitides disease
Meningitis
(meningococcemia)
Haemophilus influenzae disease
Meningitis
Mycobacterium tuberculosis disease
Tuberculosis
Bordetella pertussis disease
Pertussis (Whooping cough)
Salmonella typhi disease
Typhoid fever
Salmonella enteric disease
Salmonellosis
Vibrio cholera disease
cholera
Brucella spp. disease
Brucellosis (Undulant
fever)
Skin (Integumentary System), Parenteral pathogens
Clostridium perfringens
Rickettsia rickettsii
Clostridium perfringens disease
Gas gangrene
Rickettsia rickettsii disease
Rocky Mountain Spotted
Fever
Numbers of Invading Microbes
✓ID50
✓LD50
→compare relative virulence under experimental conditions; it is not an absolute value
✓ID50 (Infectious Dose for 50% of a sample population)
→potency of a toxin
✓LD50 (Lethal Dose for 50% of a sample population)
✓ID50 B. anthracis Cutaneous
10-50 endospores
✓ID50 B. anthracis Inhalation
10k-20k endospores
✓ID50 B. anthracis Gastrointestinal
250k-1M endospores
✓ID50 V. cholerae
108 cells (decreased upon neutralization of stomach acidity or administration of bicarbonates)
LD50 Botulinum toxin
0.03 ng/kg
LD50 Shiga toxin
250 ng/kg
LD50 Staphylococcal enterotoxin
1350 ng/kg
Host-microorganism interactions path
Encounter and entry
Colonization and entry
Invasion and dissemination
Outcome
Corresponding infection-disease stages
Incubation stage
Prodromal stage
Clinical stage
Stage of decline
Convalescent stage
Pathogen encounters and colonizes host surface
Encounter and entry
Pathogen multiplies and breaches host surface defenses
Colonization and entry
Pathogen invades deeper tissues and disseminates, encounters inflammatory and immune responses
Invasion and dissemination
Pathogen completes cycle by [outcomes]
Leaves host
Destroys host
Remains in latent state
Is destroyed by host
[stage] No signs or symptoms
Incubation stage
[stage] First signs and symptoms, pathogen may be highly communicable
Prodromal stage
[stage] Peak of characteristic signs and symptoms of infection or disease
Clinical stage
[stage] Condition of host deteriorates possibly to death or signs and symptoms begin to subside as host condition improves
Stage of decline
